The present invention relates to nanosilver particles-containing antibacterial and antifungal granules (NAGs). The nanosilver particles are attached to the surfaces and pores of stalk marrow of Juncus effusus L, which acts as an inert carrier for nanosilver. Each of the nanosilver particles contains a metallic silver core which is surrounded by silver oxide. The size of the nanosilver particle is between 1-100 nm in diameter. The present invention also relates to methods for preparing the NAGs and for using the NAGs. The NAGs can be used in a variety of healthcare, medicinal and industrial products.
Metals including silver, copper, mercury, and zinc are known for anti-bacterial properties. Bacteria treated by these metals do not acquire resistance to the metals. Therefore, the bactericidal metals have advantages over the conventional antibiotics which often cause the selection of antibiotic-resistant microorganism.
Silver is generally a safe and effective antimicrobial metal. Silver ions function in adversely affecting cellular metabolism to inhibit bacterial cell growth. When silver ions are absorbed into bacterial cells, silver ions suppress respiration, basal metabolism of the electron transfer system, and transport of substrate in the microbial cell membrane. Silver ions also inhibit bacterial growth by producing active oxygen on the surface of silver powder and silver-plated articles. Silver has been studied for antibacterial purposes in the form of powder, metal-substituted zeolite, metal-plated non-woven fabric, and crosslinked compound.
U.S. Pat. No. 5,785,972 discloses a therapeutically active composition comprising a solution of colloidal silver, helichrysum angustifolium or helichrysum italicum oil, and raw honey emulsified with water soluble lecithin. However, the contact between microbial cells and silver ions is not ensured as the silver ions quickly become eluted in the solution. Silver ions in solution are difficult to handle and therefore of limited use.
To solve the problem in liquid state, various crosslinked agents and solid supports for silver ions have been developed. For example, U.S. Pat. No. 5,709,870 discloses a silver-containing antimicrobial agent comprising a silver salt of carboxymethylcellulose and having a degree of substitution of carboxymethyl group of not less than 0.4.
Chinese Patent No. 87100231A discloses an antibacterial dressing made from nitrilon crosslinked with copper salts in alkaline medium. The resulted cloth shows antibacterial activity on ten (10) bacteria including Staphylococcus aureus (MRSA).
Japan Process Technique, Vol. 17, No. 7, teaches a nitrilon fiber manufactured from copper and sulfur salts. The fiber has bacteriostatic effects on Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Epidermophyton.
Japanese Patent No. 3-136649 discloses an anti-bacterial cloth used for washing breasts of milk cow. The Ag+ ions in AgNO3 were crosslinked with polyacrylonitrile and it had anti-bacterial activity on six (6) bacteria including Streptococcus and Staphylococcus.
Japanese Patent No. 54-151669 discloses a fiber treated with a solution of a compound of copper and silver. The solution is evenly distributed on the fiber. The fiber is used as an anti-bacterial lining inside boots, shoes, and pants.
U.S. Pat. No. 4,828,832 discloses a composition for treating skin lesions which is made up of metallic silver particles having a diameter of 1 to 10 xcexcm and an optional oxidizing agent randomly disbursed within a carrier of inert filler such as kaolin or talc.
U.S. Pat. No. 5,824,267 discloses a plastic material having a bactericidal surface on which a number of ceramic or base metal particles of a mean diameter of 0.01 to 0.5 xcexcm are embedded under the condition that a portion of each particle is exposed over the surface, and the ceramic or base metal particles have bactericidal metal particles of mean diameter of 0.0001 to 0.1 xcexcm dispersively fixed thereon.
Such solid supports using synthetic polymer materials have been not widely adapted for medical and healthcare purposes. These materials usually require bonding or cross-linking of the silver or silver ions to the polymers. Such bonding or cross-linking may invoke allergic reactions in patients. These materials also do not have sufficiently high antibacterial activity due to the lack of sufficient surface contact with the bacteria. Additionally, the bactericidal activity of these materials rapidly diminishes as the silver ions become separated from the solid supports, thus, these materials do not show bactericidal activity over a prolonged period of time. Lastly, the processes for making these materials are complicated and time-consuming.
The present invention provides nanosilver-containing antibacterial and antifungal granules (NAGs). The NAGs are made of stalk marrow of Juncus effusus L. (as a carrier) with nanosilver particles evenly dispersed on the surfaces and pores of the stalk marrow. These NAGs display longlasting bactericidal and fungicidal activities. The NAGs of the present invention are safe to use for medical and healthcare purposes as well as used in industrial products.
The present invention also provides a method for making the NAG which is suitable and feasible for large scale industrial production. The present invention is an improvement over Chinese Patent Nos. CN 1034090, CN 1093004, and CN 1123665, which are herein incorporated by reference. CN 1034090 discloses a method of attaching nanosilver particles to textile. CN 1093004 discloses a suture or medical thread containing nanosilver particles. CN 1123665 discloses a granule containing nanosilver particles attached to stalk marrow which can be used to disinfect tooth brush, for treatment of acne and pimples, and as cleansing agents to prevent gynecological infections such as vaginitis. The method for making the NAGs and the utility of using the NAGs described in the present invention are different from those described in CN 1034090, CN 1093004, and CN 1123665.
The present invention provides nanosilver-containing antibacterial and antifungal granules (NAGs) which comprise nanosilver particles which are firmly and evenly attached to stalk marrow of Juncus effusus L. The nanosilver particles are about 1-100 nm in diameter. The individual nanosilver particle has a metallic silver core surrounded by silver oxide.
The NAGs display longstanding inhibitory effect on a broad spectrum of bacteria and fungi. Examples of the bacteria and fungi include, but are not limited to, Escherichia coli, Methicillin resistant Staphylococcus aureus, Chlamydia trachomatis, Providencia stuartii, Vibrio vulnificus, Pneumobacillus, Nitrate-negative bacillus, Staphylococcus aureus, Candida albicans, Bacillus cloacae, Bacillus allantoides, Morgan""s bacillus (Salmonella morgani), Pseudomonas maltophila, Pseudomonas aeruginosa, Neisseria gonorrhoeae, Bacillus subtilis, Bacillus foecalis alkaligenes, Streptococcus hemolyticus B, Citrobacter, and Salmonella paratyphi C.
The NAGs are produced by (1) cutting the stalk marrow of Junicus effusus L. into pieces; (2) immersing the cut stalk marrow in a solution containing nanosilver particles to allow the attachment of the nanosilver particles to the cut stalk marrow; (3) after the attachment, drying the nanosilver particles-attached stalk marrow; and (4) grinding the nanosilver particles-containing stalk marrow to appropriate size to produce the NAGs. Before drying the nanosilver particles-containing stalk marrow, the stalk marrow is optionally washed with hot and cold water.
The nanosilver particles are made by dissolving silver nitrate in a solution containing concentrated ammonia water, glucose or ascorbic acid (as reducing agent), and an oxidizing agent. Optionally, NaOH can be added to the solution to adjust the pH, and ethanol can be added to the solution to improve the solubility of the solution. The preferred oxidizing agent is hydrogen peroxide (H2O2).
The present invention also provides a method for preparing the NAGs. The method comprises the following steps: (1) cutting the stalk marrow of Junicus effusus L. into pieces (about 0.5 to 2 cm at length); (2) preparing a nanosilver particles-containing solution; (3) immersing and thoroughly mixing the cut stalk marrow pieces in the nanosilver particles-containing solution to allow the attachment of the nanosilver particles to the cut stalk marrow pieces; (4) washing the cut stalk marrow pieces (preferably first with hot water, then with cold water); (5) drying the cut stalk marrow pieces; and (6) grinding the dried cut stalk marrow pieces to the desirable size(s) of the NAGs. It is preferred that the NAGs have a size which is capable of passing through a No. 200 sieve. It is preferred to boil the cut stalk marrow pieces to remove unwanted water-soluble materials, followed by heat drying the boiled stalk marrow pieces, before soaking the stalk marrow pieces in the nanosilver particle-containing solution. It is also preferred to treat the nanosilver soaked stalk marrow pieces with heat until the stalk marrow pieces turn brown, before washing the stalk marrow pieces with hot and cold water.
The nanosilver solution is prepared by the following step-wise procedure: (1) dissolving silver nitrate (AgNO3) crystal in a concentrated ammonia water solution; (2) adding glucose or ascorbic acid (as reducing agent) to the solution; and (3) adding an oxidizing agent to the solution. The preferred oxidizing agent is hydrogen peroxide (H2O2). Optionally, NaOH and ethanol can be added to the nanosilver solution to adjust the pH and improve the solubility of the nanosilver solution, respectively.
Additionally, the present invention provides methods of using the NAGs. The NAGs can be used in a variety of healthcare, medicinal, and industrial products. The NAGs can be added to ointments, lotions, and/or solutions for treating humans or animals with skin trauma, such as acne or pimples, wound, burns, skin with bacterial or fungal infections. In addition, the NAGs can be used in hygiene products, such as women gynecological washing solution, tooth brush soaking solution, or facial cleansing solution. The NAGs can also be used as food preservatives (e.g., for preserving fruits and vegetables), water disinfectants, paper disinfectants (e.g., for preventing mold build-up in book, newspaper, certificate, envelope, stationary, money, paper food containers, etc.), and in construction filling materials to prevent mold formation. Finally, the NAGs can be used as medicines to treat patients with gastrointestinal infection, sexually transmitted diseases, and eye diseases.